The present invention relates to a sensor arrangement for detecting objects with aid of an ultrasonic sensor.
A sensor arrangement of this type is disclosed in German patent document DE 20 2005 020 654 U1. The sensor arrangement described therein is used for detecting labels on a carrier material and comprises an optical sensor as well as an ultrasonic sensor, which can be activated optionally with the aid of a switching device for detecting the labels.
The optical sensor and the ultrasonic sensor operate based on the principle of the transmission measurement, meaning the transmitter and the receiver for the optical sensor on the one hand, and the ultrasonic transmitter and the ultrasonic receiver for the ultrasonic sensor on the other hand are respectively arranged on both sides of a detection plane, in which the carrier material with the labels is guided relative to the device. The sensor arrangement is arranged inside a fork-shaped housing with two fork arms, between which the detection plane extends. The components of the optical sensor and the ultrasonic sensor are arranged inside this housing so that the beam axis for the ultrasonic waves, emitted by the ultrasonic transmitter, and the optical axis for the light rays emitted by the transmitter intersect in the detection plane. As a result, the actual measuring location and the point in time for detecting the labels are not dependent on whether the ultrasonic sensor or the optical sensor is used for the detection.
Since an ultrasonic sensor or an optical sensor can optionally be used for the label detection with this type of sensor arrangement, a broad spectrum of label materials and carrier materials can be securely detected with this sensor arrangement.
The ultrasonic transmitter and the ultrasonic receiver on the one hand and the components of the optical sensor on the other hand must be arranged to be spatially offset, relative to each other, to achieve that the ultrasonic waves and the transmitted light rays intersect in a detection plane. That is to say, the beam axes for the ultrasonic waves and the transmitted light rays extend at a defined angle to each other. A considerable structural expenditure along with relatively large dimensions for the housing are therefore required to accommodate the sensor arrangement.